Abstract
Twelve male rats were individually housed in separate metabolic cages. Body weight and urinary catecholamines of the rats were measured during nine days of the isolation. Mean body weight of the rats decreased soon after transfered into the metabolic cages and thereafter increased steadily. Mean urinary level of ad-renaline was high during the early days of the isolation. The rats could be classified into two groups according to their body weight changes at the early stage of the isolation; one group showed a decrease in the body weight and the other showed a steady increase in the weight. The group with loss of the body weight showed a higher level of urinary adrenaline in the early days of isolation than that of the group with no weight loss. These results may suggest that the new environments involved in the individual caging were stressful to most of the isolated rats, and that there was an individual difference in the susceptibility to the isolation stress.
